Optical isolators, variable optical attenuators, and tap monitors are used in optical communication systems and optical measurement systems. An optical isolator allows a beam of light to pass through a device in a chosen direction, but generally prevents light from passing through the device in the opposite direction. A variable optical attenuator adjusts the power ratio between a light beam exiting the device and a light beam entering the device over a variable range. A tap monitor is used to measure the power of a light beam entering or exiting a device, or for measuring other properties of light in a device.
Although optical components are available to provide isolation, variable attenuation, and tap monitoring, it is desirable to provide an improved optical system capable of providing isolation in which the attenuation may also be varied, and/or which may also include a tap monitor for sampling light in the system.